The increasing occurrence of harmful algal blooms (HABs) in water resources worldwide is alarming the environmental and health authorities because of their potential to release biological toxins, in particular, microcystins produced from cyanobacterial HABs. Microcystins are among the most powerful natural poisons known. Exposure to microcystins can affect the number and diversity of wild animal populations, cause bioaccumulation of toxins in the tissues of fish and shellfish, and indirectly affect other organisms through the food chain and eventually humans. Methodologies for early detection or in-situ/remote sensing of outbreaks of the toxins would provide a major mechanism for reducing/preventing exposures to the toxins released by HABs. Current monitoring methods employing on-site sampling followed by in-lab analysis of HAB toxins (direct micro-observation) are neither sustainable nor practical to meet the vast spatial and temporal measuring need. Alternatively, remote sensing approaches based on identifying standard color products from satellite images (indirect macro-observation) are useful for monitoring general algal bloom activities. However, such color products are neither specific to HABs nor necessarily indicative of toxin release. As a result, it is important to determine the toxic/non-toxic nature of algal blooms and even the species of HAB toxins in a more sustainable and responsive manner. In the investigators efforts to find a complementary approach to the two different observing methods, they propose to real-time monitor the level of microcystins in-situ using an innovative wireless sensor network. Due to the lack of knowledge regarding assays of microcystins on a microscale sensor suitable for real field applications, there have been few attempts to implement the in-situ sensing idea. As a result, this study provides: 1) novel approaches to monitor toxin release during HAB activities, 2) novel ideas to quantify and qualify various microcystins at trace levels, and 3) integrated ways to realize the sensor network suitable for field applications. The investigators aim at 1) pioneering a microcystin-selective optical sensor to detect multiple microcystins at trace levels, 2) exploring an integrated chip-scale sensing node to automatically execute the sensing protocol, and 3) developing a wireless sensor network to communicate assay data and operation command between sensing nodes and remote authorities. Eventually, they will deploy the wireless sensor network in a potential HAB site in Great Lakes to monitor the spatial and temporal variation of microcystins.